Effective electrical energy audits track the right variables and provide actionable results

The pulse of the plant: An electrical energy survey provides guidance for reducing utility bills and greening of industry.

By Ross Ignall, Dranetz

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Facility professionals are finding savings opportunities by better understanding when, where and how energy is being used. It’s the necessary first step in managing utility bills. Powerful handheld instruments are ideal for facility energy studies and carbon footprint calculations, taking forward/reverse energy measurements for grid-tied alternative energy systems, and for complying with public and private-sector energy initiatives.

As the world’s largest energy consumer, the United States used around 100 quadrillion BTUs, or 105 exajoules, of energy in 2005 — three times what it was back in 1950. The U.S. Department of Energy claims that industrial and commercial buildings account for nearly 50% of that, to the tune of more than $200 billion annually. Little wonder that recent years have seen the proliferation of a bewildering array of public and private-sector energy initiatives designed to micromanage the process of increasing energy efficiency, reducing greenhouse gas emissions, mandating more stringent conservation measures and driving greater reliance on renewable energy resources.

Facility energy performance

Whether the goal is to comply with government legislation, qualify for Energy Star, LEED, Green Globes, or other rating, or simply save energy and cut cost, the tool most often used to benchmark facility energy performance, the starting point, is the energy audit. The purpose of such studies is a comprehensive evaluation of the actual performance of a plant’s systems and equipment compared to its optimal designed performance level.

The difference between observed performance and best practices is the twilight zone where potential energy and cost savings reside. Plant performance audits are vital to strong energy management programs, without which the continuous improvements of energy efficiency and its resultant cost savings are difficult to characterize. Energy audits are an extremely useful way to:

  • Identify actions for improving energy performance
  • Prioritize projects
  • Track progress.

At the operations level, it’s not unusual for large industrial and commercial power consumers to see electric bills carrying demand charges as high as 50% of the facility’s actual consumption costs. As an offset, load shedding, peak shaving, installing more efficient lighting and other energy management strategies go far toward helping plant professionals reduce demand penalties. However, before any of these strategies can be implemented, it’s necessary to gain an exact picture of how, when and where the energy is being used.

Conduct audits

The difference between observed performance and best practices is the twilight zone where potential energy and cost savings reside.

– Ross Ignall, Dranetz

As a cost-effective means for doing that, an energy audit conducted at the front end of the process helps you understand energy usage and identify areas where mitigation strategies can be implemented to cut operating costs.

As part of a strategic corporate energy management program, regular plant energy audits can be self-assessments conducted by company staff, external audits conducted by contracted energy service professionals or a combination of both. Regardless of the audit type, the audit team seems to be most effective when represented by members offering varied expertise, such as maintenance experts, systems managers and process engineers. Outside experts are especially useful for providing specific technical expertise lacking in the company.

Know what to measure

Energy audits come in many forms and can range from simple applications that monitor a single device or machine to complex monitoring of an entire campus. Regardless of a facility’s energy load, most energy audits have much in common. The most important variables to measure when analyzing electrical energy are typically voltage (V), current (I), Watts (W), volt-amperes (VA), volt-amperes reactive (VAR) and power factor (PF). Recorded over time, these basic variables can provide the necessary information for a complete energy profile.

Voltage and current measurements are used to compute the other variables. The variables can be viewed instantaneously using a variety of instruments, but the key benefit of using an energy analyzer is its ability to record and trend variables over time. Energy analyzers also compute the demand and energy that utilities use for billing. Low-cost energy analyzers offer the functionality and flexibility to perform simple-to-sophisticated energy audits that can be exported into popular software programs.

What to look for in an energy analyzer

Today’s energy analyzers are more powerful and cost-effective than ever before. Because even low-cost analyzers include the accessories and software needed to conduct a complete and user-friendly energy audit, energy analyzers are now within reach for any facilities that need to manage ever-rising energy costs.

What an energy-measuring instrument measures and computes is important, but how it measures can be critical. For example, some inexpensive, low-resolution instruments might measure the basic variables, but they can miss data and thereby produce misleading measurements.

Effective energy-analyzing instruments provide a sampling rate appropriate for the application while also capturing continuous readings. Power analyzers typically define sampling rate as the number of measurements taken per AC (60/50Hz) cycle. Because the instrument produces a digital representation of the analog voltage and current being measured, it’s generally desirable to use an instrument that provides a higher number of samples per cycle, thus resulting in more accurate data collection.

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